Wear Resistance of Ti-40Zr Alloy with TiN and ZrN Multilayer Coatings

Abstract

Production and processing of titanium alloys are expensive and its alloys show low wear resistance. Substrates of Ti-40Zr, used for orthopedic implants, were obtained from the elemental mixture of hydrogenated powders, followed by a sequence of cold uniaxial and isostatic pressing and vacuum sintering. Aiming wear resistance increase, samples were coated by physical vapor deposition using electron beam technique (EB-PVD). Multilayer coatings with three different configurations were undertaken: Ti/TiN, Ti/TiN/ZrN and Ti/TiN/ZrN/TiN. Micro-abrasive wear tests were conducted by ball-cratering, with abrasive slurry of silicon carbide (SiC). The wear craters were measured at intervals corresponding to increments in the sliding distance of approximately 14 m. Range of the normal force were between 0.35 and 0,45 N. Scanning electron microscopy was used to evaluate the wear crater and the wear mode. All experiments showed three-body abrasive wear and a reduction of one order of magnitude in wear coefficient for two coated samples: 2,58∙10-12m³(Nm)-1to substrate, 5,4∙10-13m³(Nm)-1to Ti+TiN film and 7,22∙10-13m³(Nm)-1to Ti+TiN+ZrN film. In the Ti+TiN+ZrN+TiN experiment the wear coefficient of film is nearer to the substrate, 7,58∙10-13m³(Nm)-1. The multi-layers containing ZrN presented wear coefficient higher than Ti/TiN films, possibly due to existing residual stresses.